MRK · Merck & Co., Inc.

The thesis

Merck's newer medicines are growing fast enough to start reducing its dependence on Keytruda, and the third-quarter report on 29 October 2026 settles the next step of the case. That report shows whether sales track the raised full-year 2026 range of $66.3–67.3 billion. It also gives the first full quarter of sales for Lipfendra, the oral cholesterol pill the Food and Drug Administration (FDA) approved on 16 July 2026.

Since the last update, the new facts are mixed. On 7 October 2026 a Dutch patent court barred Merck's European unit from making or selling the under-the-skin form of Keytruda in eight European markets, per Halozyme and pharmaphorum. On the other side, Cantor Fitzgerald raised its target on 8 October 2026, and Morgan Stanley kept an Overweight rating despite a lower target. Neither change touches the near-term question, which is whether Winrevair, Welireg, Capvaxive and Lipfendra keep growing in the third quarter.

Keytruda and its under-the-skin form, Keytruda Qlex, brought in $8.4 billion of that, also up 5%. Winrevair rose 75% to $588 million, Welireg rose 67% to $271 million and Capvaxive rose 42% to $184 million.

Bullish and bearish views on Merck & Co., Inc.

The bull case on Merck & Co., Inc. (MRK), in brief: Newer products are growing fast. The bear case: Keytruda still dominates sales.

Bull case

• Newer products are growing fast. Winrevair sales rose 75% and Welireg sales rose 67% in the second quarter of 2026, per Merck's 4 August 2026 results.
• Merck raised its revenue outlook. On 4 August 2026 Merck lifted full-year 2026 sales guidance to $66.3–67.3 billion, from $65.8–67.0 billion.
• A new heart-health product is launching. The FDA approved Lipfendra (enlicitide) on 16 July 2026; Merck calls it the first once-daily oral PCSK9 inhibitor for lowering LDL cholesterol. It cut LDL cholesterol by 56% against placebo at week 24 in the Phase 3 CORALreef Lipids trial, per Merck.
• A dense month of regulatory wins. The FDA approved Welireg plus Lenvima for advanced kidney cancer on 24 September 2026 and updated Winrevair's label on 22 September 2026 using the Phase 3 HYPERION trial. Japan approved Keytruda Qlex for all existing Keytruda uses on 21 September 2026.
• Positive mid-stage immunology data. On 30 September 2026 Merck said tulisokibart met its Phase 2b primary endpoint in hidradenitis suppurativa, a chronic skin disease, with response rates of 72% and 64% at two doses against 35% for placebo at week 16.
• Cancer vaccine work is moving toward launch. Tempus said on 7 October 2026 it expanded its collaboration with Merck and Moderna to support sample collection and genetic sequencing for the potential commercialization of the cancer vaccine intismeran autogene alongside Keytruda; terms were not disclosed.
• Most analyst targets sit above the share price. JPMorgan raised its target to $165 from $150 on 5 October 2026, and Scotiabank raised its target to $180 from $155 on 29 September 2026. Morgan Stanley lowered its target to $177 on 7 October 2026 but kept an Overweight rating, per Benzinga.

Bear case

• Keytruda still dominates sales. Keytruda and Keytruda Qlex made up $8.4 billion of $16.6 billion in second-quarter 2026 sales, per Merck. Its patent expiry is the central long-term risk for the company.
• A patent ruling blocks the new Keytruda form in Europe. On 7 October 2026 the Hague patent court found Merck infringed Halozyme's patent EP 2,797,622 and barred the under-the-skin form of Keytruda in Belgium, Denmark, France, Ireland, Italy, Sweden, Switzerland and the Netherlands, per Halozyme. A German court already blocked it on 4 December 2025, and Halozyme is also suing in US federal court in New Jersey. The intravenous form stays available. The under-the-skin form sold $463 million worldwide in the second quarter, per pharmaphorum.
• A vaccine rival posted Phase 3 data. Vaxcyte said on 5 October 2026 that VAX-31 met noninferiority against Capvaxive on 17 of 19 shared serotypes in the 4,047-person OPUS-1 trial. Vaxcyte plans its US filing in the first half of 2028.
• Deal charges halved the profit outlook. On 4 August 2026 Merck cut full-year non-GAAP (adjusted) earnings-per-share guidance to $2.66–2.76 from $5.04–5.16, mainly on a $2.31 per share charge for the Terns acquisition.
• A late-stage cancer filing was withdrawn. Merck and Daiichi Sankyo withdrew the US application for ifinatamab deruxtecan in small cell lung cancer on 25 September 2026 after FDA feedback on Phase 2 data.
• Some analysts see little upside. Cantor Fitzgerald kept a Neutral rating while raising its target to $145 on 8 October 2026, per Benzinga, close to the $142.38 close that day.

Price setup

The shares closed at $142.38 on 8 October 2026 on adjusted daily closes, 8.5% below the 52-week high of $155.53 and 15.5% higher over three months. The 14-day relative strength index (RSI), a momentum gauge running from 0 to 100, stood at 40.2, which points to fading short-term momentum without an oversold reading.

The $134 level marks the point where a large part of the three-month advance would be undone. A close there would show the market discounting the newer-product story ahead of, or in response to, the third-quarter report. The observable crowding signal is the earnings date 20 days out; the shares sit below their high and momentum has cooled.

Catalysts, next 30 days

• 26 October 2026 — Merck investor event at the ESMO 2026 oncology congress. It shows how management frames the cancer pipeline after the 25 September 2026 withdrawal and the 7 October 2026 European patent ruling.
• 29 October 2026 — Third-quarter 2026 sales and earnings report, call at 9:00 a.m. ET, per Merck. It shows whether Winrevair, Welireg and Capvaxive keep growing, gives the first full-quarter read on Lipfendra, and confirms or cuts the $66.3–67.3 billion sales range. It may also give Merck's first quantified view of the European patent ruling.

What would change the view

The case breaks if the 29 October 2026 report cuts the $66.3–67.3 billion full-year sales range, or if Winrevair and Welireg growth slows sharply from the second quarter's 75% and 67%. A daily close below $134 would also end it, because that would undo a large part of the three-month advance.

A wider loss on the Halozyme patents, such as a US court injunction against Keytruda Qlex, would weaken the plan to move patients to the under-the-skin form before Keytruda's patents expire. Another withdrawn filing or failed Phase 3 trial in a late-stage cancer program would weaken it further.

What it trades with

Merck trades with large US drugmakers and the defensive health-care sector, so sector rotation into or out of defensive stocks moves it alongside peers. Company-specific swings now come from competitor and legal news: Vaxcyte's pneumococcal vaccine data, PD-1/VEGF cancer drugs such as Summit and Akeso's ivonescimab, and Halozyme's patent cases. Halozyme shares tend to move opposite Merck on rulings in that dispute.